One side of an old debate may have some brand new evidence. A joint study between Bristol and Newcastle Universities, involving thousands of children, purports to show no link between visual disorders and dyslexia, a common learning disability.
The link itself is a long-time bone of contention for physicians and educators. However, a growing body of evidence has been pointing more and more firmly to there being no actionable connection between the two. The most recent study, among the largest on the subject, found that dyslexic children were no more likely than their peers to have visual disorders.
While opponents have fired back, lead researchers and their supporters have taken aim at practitioners who seek to remedy dyslexia with vision therapy. At this point though, we’ll take some time to start from the top of the debate, beginning with:
Dyslexia is an umbrella term, loosely covering a wide range of disorders that impair a person’s ability to read. Dyslexia doesn’t affect intelligence, but people with the disorder nevertheless have difficulty with different reading-related tasks, such as sounding out words, writing, or distinguishing letters quickly.
These problems are enormously widespread and occur on a spectrum. Most sources estimate a prevalence of around three to four percent, with this Chinese study published in PLOS ONE being fairly representative.
While the actual effects of dyslexia are extremely varied, most make reading and associated tasks much more difficult for dyslexics. Although adults with the condition are often proficient – if slower – readers, younger dyslexics often find school a much more challenging and frustrating experience than their peers. Consequently, catching and treating the disorder early is key.
Once dyslexia is diagnosed, therapy begins. What this actually looks like depends heavily on the person who supposedly benefits from it; dyslexia comes in such a wide range of forms that each individual with the condition will likely have their own particular set of needs.
Practicing to gain proficiency with particular problems areas does have proven benefit, especially if therapy starts early, while a child’s brain is still developing. Interventions that work on relating letters to sounds have been widely adopted. More recently, other tricks and hacks have sprung up. Dyslexic designers have created several typefaces that are specifically created to remove some of the elements that normally become muddied by the condition.
The Vision Problem
All well and good? Not quite. For years, a vocal minority of physicians have advocated for the use of visual therapy to treat dyslexia. Recent years have seen this group become smaller and smaller, as more and more evidence piles up to support the theory of dyslexia being based in the brain, not the eyes.
At this point, popular and official opinion is generally that vision therapy has little use in the treatment of dyslexia. However, as many therapists are quick to point out, it does have its place in treating vision problems that can mimic dyslexia.
And these absolutely do exist. Convergence disorders – defects in how a child’s eyes work together to perceive detail – are common and can present themselves in similar ways to dyslexia. Convergence insufficiency, in which eyes have difficulty moving toward one another when focusing on near work, can make reading extremely tough as words stubbornly remain blurry.
Children with these disorders will generally wind up slower readers, something that can get them an understandable, but incorrect dyslexia diagnosis. These shared characteristics have lead some physicians to shift their stance on dyslexia. While they might still believe in a visual basis for dyslexia, they also acknowledge other aspects. For example, after the findings of the Bristol/Newcastle study were released, Professor Bruce Evans, research director for the Institute of Optometry said this in response:
Unfortunately, the authors’ tendency to reduce their test results to pass/fail seems to extend to their conclusions, where they only seem to consider two options: visual problems cause dyslexia or visual problems are irrelevant to dyslexia… In a few cases, visual factors add to the disability and then a visual treatment, for example, glasses, eye exercises or coloured filters, will give the child better access to the extra teaching that they no doubt will also need.
What’s It All Mean?
On the face of things, the study seems open and shut. Dr. Cathy Williams, the lead researcher on the recent study, summed up the report by pointing out that, in thousands of cases, dyslexic children were no more likely than non-dyslexic children to have visual disorders.
It seems pretty definitive. However, Evans’ response does bring up an important point: it’s vital to realize that a disorder can have more than one contributing factor.
Dyslexia may not entirely originate from visual disorders, but it can certainly still be accompanied or exacerbated by them. Therapy that might be effective for a majority of dyslexics might falter for the still large minority that do have complicating visual problems. In short, we shouldn’t be so quick to put the visual theory to bed that we forget that for at least some cases, it’s still absolutely relevant.
Finally, we also shouldn’t let dyslexia overshadow the diagnosis of common visual difficulties that can imitate it. Convergence insufficiencies are far from rare, and children with them are already apt to slip through screenings undetected. It’s a problem we can’t afford to cloud with one-size-fits-all diagnoses of dyslexia.